diff --git a/hosts/common/programs/mpv/default.nix b/hosts/common/programs/mpv/default.nix
index 8b870779..a2af4612 100644
--- a/hosts/common/programs/mpv/default.nix
+++ b/hosts/common/programs/mpv/default.nix
@@ -96,7 +96,9 @@ let
       ### is hard to adjust while screen is on.
       ### note that only under alsa (`-ao=alsa`) does `ao-volume` actually correspond to system volume.
       substituteInPlace src/uosc/main.lua \
-        --replace-fail "mp.observe_property('volume'" "mp.observe_property('ao-volume'"
+        --replace-fail \
+          "mp.observe_property('volume', 'number', create_state_setter('volume'))" \
+          "mp.observe_property('volume', 'number', update_ao_volume)"
       substituteInPlace src/uosc/elements/Volume.lua \
         --replace-fail "mp.commandv('set', 'volume'" "mp.commandv('set', 'ao-volume'" \
         --replace-fail "mp.set_property_native('volume'" "mp.set_property('ao-volume'"
@@ -107,14 +109,20 @@ let
       # in the meantime, just query the volume every tick (i.e. frame).
       # alternative is mpv's JSON IPC feature, where i could notify its socket whenever pipewire volume changes.
       cat <<EOF >> src/uosc/main.lua
-      function update_ao_volume()
-        local vol = mp.get_property('ao-volume')
-        if vol ~= nil then
+      function update_ao_volume(_, vol)
+        if vol == nil then
+          -- vol will be nil if called manually, instead of via observe_property
+          vol = mp.get_property('ao-volume')
+        end
+        if vol == nil then
+          vol = 0
+        else
           vol = tonumber(vol)
-          if vol ~= state.volume then
-            set_state('volume', vol)
-            request_render()
-          end
+        end
+
+        if vol ~= state.volume then
+          set_state('volume', vol)
+          request_render()
         end
       end
       -- tick seems to occur on every redraw (even when volume is hidden).
@@ -124,9 +132,6 @@ let
       mp.add_periodic_timer(2, update_ao_volume)
       -- invoke immediately to ensure state.volume is non-nil
       update_ao_volume()
-      if state.volume == nil then
-        state.volume = 0
-      end
       EOF
     '';
   });